TYPO3 is, along with Drupal, Joomla! and WordPress, among the most popular content management systems worldwide, however it is more widespread in Europe than in other regions. The biggest market share can be found in German-speaking countries.[2][3]

TYPO3 is credited to be highly flexible. It can be extended by new functions without writing any program code. Also, the software is available in more than 50 languages and has a built-in localization system, therefore supports publishing content in multiple languages. Due to its features, scalability and maturity, TYPO3 is used to build and manage websites of different types and size ranges, from small sites for individuals or nonprofit organizations to multilingual enterprise solutions for large corporations. According to the ability to support a corporate environment, it is classified as an enterprise level content management system.[4][5]

TYPO3 was initially authored by the Dane Kasper Skårhøj in 1997.[6] It is now developed by two teams. The maintenance (versions 4.x, 6 and newer) tree's team leader is Oliver Hader. The development (TYPO3 Neos) tree's team leader is Robert Lemke.[7]

Latest calculations from the TYPO3 Association claim that it is currently used in more than 500,000 installations. However the number of installations crawled by the public website "CMS Crawler" was around 270,000 by July 2013.[3][8]

Delivered with a base set of interfaces, functions and modules, TYPO3's functionality spectrum is implemented by extensions. More than 5000 extensions are currently available for TYPO3 for download under the GNU General Public License from a repository called the TYPO3 Extension Repository, or TER.[9]

TYPO3 can run on most HTTP servers such as Apache or IIS on top of Linux, Microsoft Windows or Mac OS X. It uses PHP 5.3 or newer and any relational database supported by the TYPO3 DBAL including MySQL, Oracle, PostgreSQL, and others. Some 3rd-party extensions - not using the database API - support MySQL as the only database engine. The system can be run on any web server with a modern CPU and at least 256 MB RAM. The backend can be displayed in any modern browser with JavaScript. There is no browser restriction for displaying user-oriented content generated by TYPO3.

Conceptually, TYPO3 consists of two parts: the frontend, visible to visitors, and the administrative backend. The frontend displays the web content. The backend is responsible for administration and managing content. The core functions of TYPO3 include user privileges and user roles, timed display control of content (show/hide content elements), a search function for static and dynamic content, search-engine friendly URLs, an automatic sitemap, multi-language capability for frontend and backend, and more.

Like most modern CMSes, TYPO3 follows the policy of separation of content and layout: The website content is stored in a relational database, while the page templates are stored on the file system. Therefore both can be managed and updated separately.

TYPO3 defines various basic types of content data. Standard content elements are described as text, text with media, images, (plain) HTML, video etc. Various additional types of content elements can be handled using extensions.

The fundamental content unit is a "page". Pages represent a URL in the frontend and are organized hierarchically in the backends' page tree. Standard pages serve as "containers" for one or multiple content elements. There are several additional special page types:

shortcuts (they show content from another page)

mount points (that insert a part of the page tree at the mount point)

external URLs

system folders (to handle complex data such as registered users)

…and more

Internally, TYPO3 is managed by various PHP arrays. They contain all the information necessary to generate HTML code from the content stored in the database. This is achieved by a unique configuration language called TypoScript.

Designing and developing with TYPO3 is commonly based on the following elements, among others:

Page tree

Representation of all pages of a site, their structure and properties

Constants

System-wide configuration parameters

Template

Traditionally, a simple HTML skeleton with markers (e.g., „###MARKER###“) and range markers, called subparts (e.g., „<!-- ###CONTENT### Start --> … <!-- ###CONTENT### End -->“); that are replaced by various content elements: navigation, text, graphics etc.) or serve as a subtemplate. Since TYPO3 4.3, the new template engine Fluid can be used.

As TYPO3 CMS is written in PHP, therefore most features can be modified or extended by experienced users. Mentionable here is the XCLASS mechanism, by which classes and methods can be overwritten and extended. If available, hooks are preferred.

TypoScript is a purely declarative configuration language. In Typoscript, configuration values are defined, which are parsed into a system-wide PHP array. TypoScript is object-based and organized in a tree-like structure.

TypoScript Template: The section associated with generating frontend output is called TypoScript Template. Its main use is to generate HTML code, possibly based on one or more HTML templates. The array controls the functions that, for example, are executed when the page is rendered in the frontend. Therefore it enables developers to globally manage features and extensions for the entire website with just a few modifications. Simplified: By creating an object in TypoScript, the system is instructed to execute several PHP functions, which create the desired output.[10]

TSconfig: TypoScript also influences the backend and other aspects of a TYPO3 project. The TSconfig branch of the TypoScript tree consists of User TSconfig and Page TSconfig. It's built by the same syntax as the TypoScript Template described above.[11]

Basic syntax:

[objectpath].[attribute] [operator] [value]

Operators include:

= assign a value

< copy an object

=< insert a reference to an object

> delete an object

Example:

In order to create any output at all, at least a PAGE-object has to be defined. Using the following code will render the text "Hello World" in the frontend, wrapped in <h2> HTML tags:

Extensions are the cornerstone in the internal architecture of TYPO3. A feature that was introduced with version 3.5 in 2003 is the Extension Manager, a control center managing all TYPO3 extensions. The division between the TYPO3 core and the extensions is an important concept which determined the development of TYPO3 in the past years. Extensions are designed in a way so they can supplement the core seamlessly. This means that a TYPO3 system will appear as a unit while actually being composed of the core application and a set of extensions providing various features.[13]

Diagram of the basic TYPO3 system architecture

They can be downloaded from the online repository (TER) directly from the backend, and are installed and updated with a few clicks. Every extension is identified by a unique extension key (for example, tt_news). Also, developers can share new or modified extensions by uploading them to the repository.[9]

Generally, extensions are written in PHP. The full command set of PHP 5.3 can be used (regarded the system requirements of the specific TYPO3 version), but TYPO3 also provides several library classes for better efficiency: Best known and most used is the piBase library class. With introduction of TYPO3 4.3 in 2009, piBase has been replaced (or extended) by the Extbase library, which is a modern, MVC-based development framework. To ensure backwards compatibility, both libraries can be used in the same TYPO3 installation. Extbase itself is a backport of some features of FLOW3, a general web application framework and also the base for future versions of TYPO3 (see TYPO3 Neos)[14]

A completely rewritten version (working title "Phoenix") was originally planned as TYPO3 version 5.0. While working on this new release and analyzing the 10-year history and complexity of TYPO3 v4, the TYPO3 community decided to publish version 5 as a completely new product that cannot replace version 4 in the near future, and therefore needs to have its own name. Phoenix is based on FLOW3 and various other packages and will be released in late 2012.[62][63]

Starting with the new version, the TYPO3 Association asked all contributors to sign an individual Contributor License Agreement (CLA). Signing such an agreement is not necessary, but recommended.[64] This recommendation is common practice. it is also used by Zend Framework, Apache, Yahoo and other software publishers[65][66][67][68]

In September 2012, the TYPO3 developers decided on the final name for the new product, "TYPO3 Neos".[69] With TYPO3 Neos 1.0 alpha1, a public test version was released in late 2012.[70][71]